JPH08108615A - Ink-jet recording sheet and its manufacture - Google Patents

Abstract

PURPOSE: To obtain excellent image color properties, by a method wherein at least two layers of ink receptive layers are provided on a substrate, an amount of coating of the ink receptive layer as an undercoating layer adjoining to the ink reception layer of the uppermost layer is taken as at least a specific amount, and the ink receptive layer of the uppermost layer is applied onto the ink receptive layer of the undercoating layer in a wet state, and dried in a specific condition. CONSTITUTION: An ink-jet recording sheet has at least two layers of an ink receptive layers on a substrate. An ink receptive layer of an undercoating layer adjoining to the ink receptive layer of the uppermost layer is applied to the ink receptive layer to the uppermost layer at a coating amount of at least 4g/m<2> . The ink receptive layer of the uppermost layer is applied onto the ink receptive layer of the undercoating layer in a wet state by a curtain coating device and dried during a period from application of the ink receptive layer of the undercoating layer to the application of the ink receptive layer of the uppermost layer, that is within a dwell time of 5 seconds. Since coating of the outermost layer is performed within a specific dwell time, infiltration of a binder component of the outermost layer into the undercoating layer is controlled, thus uniformizing the distribution of the binder in the outermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet for recording with an ink and a method for producing the same, and more specifically, it provides excellent image density unevenness due to excellent dot diameter variation rate and dot roundness. In particular, the present invention relates to an inkjet recording sheet having high printing density and excellent image colorability, and a method for producing an inkjet recording sheet that can be manufactured without coating defects.

[0002]

2. Description of the Related Art The ink jet recording system is a system in which minute droplets of ink are ejected by various operating principles to adhere to a recording sheet such as paper to record images, characters, etc., but at high speed and low noise. It is characterized by easy multicoloring, high flexibility in recording patterns, and no need for development-fixing, and is rapidly spreading in various applications as a recording device for various figures and color images including Chinese characters. Furthermore,
An image formed by the multicolor inkjet system can obtain a print comparable to that of the multicolor printing by the plate making system or the printing by the color photographic system. Further, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is cheaper than the photographic technique.

As a recording sheet used in this ink jet recording system, efforts have been made from the viewpoint of the apparatus and the ink composition in order to use high-quality paper or coated paper which is used for ordinary printing and writing. However, with the improvement of the performance of the inkjet recording apparatus and the expansion of the application such as the speeding up and the definition of the apparatus or the full colorization, more advanced characteristics are required for the recording sheet. That is, as the recording sheet, the density of the print dots is high and the color tone is bright and vivid, the ink does not flow out or bleed even when the print dots are overlapped quickly, and the horizontal direction of the print dots Is required to be high in image reproducibility, such as that the diffusion is not unnecessarily large and the periphery is smooth and does not blur.

Several proposals have hitherto been made in response to such demands. For example, JP-A-52-907
JP-A No. 4 and JP-A No. 58-72495 disclose a device for improving ink absorbability by providing an ink receiving layer which is a void layer containing a silica-based pigment as a main component on the surface of a support. In order to increase the ink absorbability by this ink receiving layer and obtain a print dot without high print dot density and ink bleeding, JP-A-55-51583 and JP-A-56-157 disclose non-colloidal silica. There is a proposal to mix powder. Further, JP-A-55-144172 proposes the use of a specific agent that adsorbs a dye component, paying attention to the fact that the dye in the ink is in a state of distribution in the ink receiving layer with respect to color and sharpness. It has been done.

However, when the ink receiving layer has a low coating amount of about 1 to 10 g / m ² , the printed ink cannot be received only by the ink receiving layer, and the ink absorbability is also absorbed by the support. Is required. For this reason, the support is required to have a low size property, but when a low size support is used, the ink absorbability is good, but the ink penetrates deeply in the thickness direction of the support, and the problem of strikethrough occurs. Occurs. Further, the ink is diffused in the surface direction of the support to cause deterioration of the dot shape called feathering, which is jagged like bird feathers.

On the other hand, in order to suppress the permeation of the ink in the ink receiving layer, if the coating amount is increased to increase the ink absorption,
Although strike-through and feathering can be suppressed, the adhesiveness of the ink receiving layer and powder drop easily occur. Furthermore, in the coating step of forming an ink receiving layer on the surface of a water-absorbing support, the binder or solvent (mainly water) in the ink receiving layer coating composition penetrates into the support, or the ink is used in the drying step. The binder moves to the surface of the receiving layer. As a result, the binder distribution in the surface direction and the thickness direction of the ink receiving layer becomes more uneven, the ink absorption becomes uneven, and the dot shape becomes uneven. If the coating amount is less than 1 g / m ² , the effect of the ink receiving layer is difficult to obtain.

Further, suppressing the permeation of ink without increasing the ink receiving layer is in agreement with reducing the amount of voids in the ink receiving layer, and as a result, the amount of voids in the ink receiving layer is reduced, thereby reducing the ink receiving layer. Infiltration of the ink into the layers and the support is delayed, the ink becomes undried, and in the heavy color area where dots are printed by overlapping the ink, the ink may overflow around the dots or while the sheet is being conveyed in the inkjet recording device. ,
The dots rub against each other in contact with a device around the carrying device, which causes a rubbing stain called a background stain. If this rubbing stain is generated over a wide area, not only the non-image area will become dirty and spoil the appearance, but also if the area is extremely narrow, adjacent dots will come into contact with each other, resulting in a decrease in sharpness due to the enlargement of the dots and coloration due to color mixing. And the image reproducibility is greatly deteriorated.

Furthermore, when a metering type coating device or a roll coating device, which has been conventionally used for coating the ink receiving layer coating liquid, is separated from the liquid supplying part and the measuring part, the structure of the ink receiving layer is high. It was not possible to obtain an ink jet recording sheet having an ink receiving layer satisfying the condition of.

That is, when the blade coating method or the rod coating method is used, an ink receiving layer having a relatively smooth surface shape can be obtained, but a paper produced by making pulp or synthetic fiber into paper is used as a support. Then, uneven coating amount corresponding to the surface shape of the support occurs. Further, in such a coating method, coating defects such as streaks and scratches are likely to occur in the operation of the coating layer, and an ink receiving layer having a uniform coating amount cannot be obtained.

Further, in such a coating method, the binder component in the coating liquid is excessively infiltrated into the web between the supply of the excess coating liquid and the measurement, and further coating is carried out at the blade tip portion or the rod contact portion. Since a high pressure is applied to the liquid, the penetration of the binder proceeds further. This is
Not only does the image density and sharpness decrease, but the coating liquid scraped off as an excess is different from the composition of the coating liquid before supply, so the composition of the coating liquid changes over time,
It is not possible to obtain stable quality products.

In the air knife coating method, it is inevitable that a pattern peculiar to the air knife is generated in the coating layer, and an ink receiving layer having a uniform coating amount cannot be obtained. Similarly, even in various roll coating apparatuses, when the coating liquid is transferred from the roll to the support, it is inevitable that a coating amount unevenness called a split pattern occurs.

Further, high absorbency, which is difficult to obtain with a single-layer coated product,
In order to obtain the image quality of the ink jet recording sheet such as dot roundness and print density, it is possible to coat two or more ink receiving layers and satisfy these requirements, but it is possible to use two or more layers offline. The application of the ink receiving layer is not only disadvantageous in terms of operability, but also the undercoating ink receiving layer (hereinafter, referred to as a support) for applying the uppermost ink receiving layer (hereinafter, abbreviated as the uppermost layer) is applied. Since it is necessary to use a high-absorption pigment also in the undercoat layer),
Excessive penetration of the solvent components (water, binder, etc.) in the coating composition of the uppermost layer into the undercoat layer requires an excess binder component in the uppermost layer to obtain the required coating layer strength. As a result, the ink jet recording apparatus increases the collision resistance of the ink when printed on the sheet, which causes an increase in the dot diameter, a deterioration in the dot shape, and a reduction in the print density due to the increase in the ink jet recording sheet. Not good for image quality.

Further, due to the recent increase in the speed of ink jet recording apparatuses, it becomes necessary to obtain high quality ink jet paper image quality such as high absorbency, dot roundness and print density. However, an increase in the coating amount of the ink receiving layer or an increase in the porosity of the ink receiving layer to satisfy these factors makes it easier for the adhesiveness of the ink receiving layer and powder drop to occur. There is difficulty to make it. Further, the image quality required of the inkjet recording sheet is increasing more and more, and in particular, the demand level for sharpness and color is rapidly increasing.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording sheet which has a high variation in image density, a high printing density, and an excellent image colorability due to excellent dot diameter variation rate and dot roundness. Another object of the present invention is to provide a method for manufacturing an inkjet recording sheet that can be manufactured without coating defects.

[0015]

As a result of intensive studies in view of the above, the present inventors have invented the ink jet recording sheet of the present invention and the manufacturing method thereof. That is, in the inkjet recording sheet of the present invention, the coating amount of the ink receiving layer as an undercoat layer adjacent to the uppermost ink receiving layer is 4
g / m ² or more, and at least ² that the uppermost ink-receiving layer is applied to the wet ink-receiving undercoating layer by a curtain coating device within a dwell time of 5 seconds and dried.
It is characterized in that it has at least two ink receiving layers on a support.

The method for producing an ink jet recording sheet of the present invention is the same as the method for producing an ink jet recording sheet in which at least two or more ink receiving layers are provided on a support, and an undercoat layer adjacent to the uppermost ink receiving layer is provided. The ink receiving layer as a layer is applied at a coating amount of 4 g / m ² or more, and the uppermost ink receiving layer is curtain-applied on the undried ink receiving layer of the undercoat layer within a dwell time of 5 seconds. It is characterized in that it is applied and then dried.

The ink jet recording sheet of the present invention and the method for producing the same will be described below in detail.

In the present invention, the dwell time means the time from the application of the ink receiving layer of the undercoat layer to which the ink receiving layer of the uppermost layer is adjacent to the coating of the ink receiving layer of the uppermost layer on the support. It means the time. At this time, the ink receiving layer of the undercoat layer is undried, that is, in a wet state, and the drying step is started only after the uppermost ink receiving layer is applied. In the present invention, a satisfactory inkjet recording sheet can be obtained when the dwell time is within 5 seconds.

The reason why the uppermost layer is applied within the specific dwell time on the undercoat layer in a wet state is based on the following reasons. Since the ink jet recording sheet is required to have good ink absorbability, a highly absorbent pigment such as a porous silica pigment is often used in the undercoat layer. Therefore, after drying the undercoat layer using a large amount of the high-absorbent pigment, when the uppermost layer is applied, the water-soluble binder component together with the water, which is the solvent of the coating composition of the uppermost layer, also excessively penetrates into the undercoat layer. Due to problems such as lower adhesion of the receiving layer and powder drop of the coating layer, the smoothness of the support that coats the undercoat layer, uneven thickness of the undercoat layer, etc. The penetration of the water-soluble binder is not uniform at all. Therefore, the distribution of the binder in the uppermost layer becomes non-uniform, and the dot diameter varies, which adversely affects the quality of the inkjet recording sheet.

In the present invention, after the undercoat layer has been applied, the uppermost layer is applied without a drying step, so that the presence of water in the undercoat coating film suppresses the penetration of the water-soluble binder component in the uppermost layer. , The binder dose can be reduced and
The binder distribution in the uppermost layer is also uniform, resulting in an excessive increase in dot diameter, variation in dot diameter, deterioration of dot shape,
In addition, it is possible to improve the decrease in printing density.

In the present invention, the dwell time can be controlled by changing the line speed and the distance from the completion of coating the undercoat layer to the coating of the uppermost layer (hereinafter referred to as 1C-2C distance). The line speed and the 1C-2C distance are not particularly limited as long as the dwell time is within 5 seconds, but the line speed is preferably 50 to 1000.
When the m / min, 1C-2C distance is 1 to 30 m, it is possible to select the desired dwell time.

Furthermore, by using a curtain coating device which is a pre-weighing type coating device for the coating method of the uppermost layer,
The measurement of the liquid is completed before the coating on the support, and when the topcoat layer is provided on the undercoat layer in a wet state with a coating device such as a blade, rod, or air, the boundary between the undercoat layer and the topcoat layer It is possible to prevent problems such as disorder and mixing of the overcoat layer and the undercoat layer. Further, since the curtain film has free surfaces on both sides, one side of the curtain film is stretched by contact with the support at the time of coating to form a coating layer film.
Since a uniform liquid film is stretched to form a coating layer film without being regulated by the flow path during coating, the coating layer film has an extremely uniform thickness regardless of the shape of the support. Furthermore,
Since there is almost no pressure applied to the support and the coating liquid during curtain coating, the porosity of the ink receiving layer and the support is not reduced. It has been found that as a result, the binder component in the uppermost layer can be made uniform, high ink absorbency can be secured, and the quality of the inkjet recording sheet can be improved.

However, in curtain coating, a coating failure phenomenon called an air entrainment phenomenon in which air penetrates between the coating layer film and the surface of the support may be observed. When the air entrainment phenomenon occurs, the entrained air becomes bubbles, expands in the drying process, penetrates the coating layer, and forms bubble marks without the coating layer. Further, in particular, when the amount of entrained air is large, the coating layer becomes distributed in a sea-island shape on the surface of the support. The uneven coating amount distribution of the ink receiving layer which occurs as described above causes unevenness in image density and lack thereof, and it is not possible to obtain an inkjet recording sheet of a satisfactory quality.

In an ink jet recording sheet in which at least two or more ink receiving layers are coated on the support of the present invention, when the coating amount of the undercoat layer is 4 g / m ² or less,
Since the thickness of the wet coating film of the undercoat layer is thin, the roughness of the support for coating the undercoat layer and the pigment particles in the undercoat layer deteriorate the smoothness of the surface of the wet coating film of the undercoat layer.
Even when the dwell time is 5 seconds or more, the solvent component of the undercoat layer is absorbed by the support over time due to the absorbability of the support itself on which the undercoat layer is coated, and the nonuniform solvent of the support itself is absorbed. The absorption and the pigment in the undercoat layer gradually deteriorate the smoothness of the surface of the undercoat layer.

When the uppermost layer is coated on the roughened undercoating layer having a deteriorated smoothness by using a curtain coating device without pressure load, air penetrates into the concave portion of the surface of the undercoating layer and the coating is caused by an air entrainment phenomenon. Failure phenomenon occurs.

Furthermore, when the curtain-coated support is provided with a coating layer made of a pigment, an adhesive, etc. and has low air permeability, the smoothness of the curtain-coated support is an extremely important factor. It becomes one. Therefore, the coating amount of the undercoat layer on which the uppermost layer is applied is set to 4 g / m ² or more, and the dwell time is set to 5 seconds or less without a drying step, so that there is no coating failure and printing quality and image colorability are excellent. It was found that a multi-layer coating inkjet recording sheet was obtained.

The coating amount of the uppermost layer is not particularly limited, but if it is too small, the ink absorbability is good as in the case of the non-coat type ink jet recording sheet.
Feathering occurs due to low image density, color and sharpness. Further, if the coating amount is too large, the drying load in the drying step after coating increases, and not only the productivity decreases due to the reduction of the coating or impregnation speed, but also the coating forming the ink receiving layer in the case of drying at a high load. The binder in the composition moves to the surface of the ink receiving layer together with the solvent that evaporates, and the amount of voids on the surface is reduced, so that scumming occurs during recording. The problem that occurs in the ink receiving layer with a large coating amount is
Although it is affected by the concentration of the coating composition and the ability of the drying process, it is preferably 5 to 15 g / m ² . Further, in the present invention, a back coat layer may be provided. The coating amount of the back coat layer is not particularly limited, and it is desirable to select it in accordance with the device for coating or impregnating and the capability of the drying process.

The support used in the present invention is composed mainly of wood pulp and a pigment, and one or more coating layers adjacent to paper made of wood pulp may be provided by various coating or impregnating machines. . As wood pulp, LBK
Chemical pulp such as P, NBKP, GP, PGW, RM
P, TMP, CTMP, CMP, mechanical pulp such as CGP, pulp such as waste paper pulp such as DIP, conventionally known pigments and binders and sizing agents and fixing agents, yield improvers, cationizing agents, It is possible to mix various types of additives such as paper strengthening agents with one or more types, and to manufacture the support with various devices such as Fourdrinier paper machine, cylinder paper machine, twin wire paper machine, acidic, neutral It can be made with alkaline paper. An undercoat layer may be provided on the support as it is, or an ink receiving layer may be provided after a size press using starch, polyvinyl alcohol or the like or at least one anchor coat layer is provided.

The support is preferably subjected to on-machine treatment with a device such as a soft calendar or a machine calender, but may be subjected to off-machine treatment with a device such as a super calender. ,
The flatness may be controlled by calendering with a super calender, but considering ink penetration, the density after calendering is 0.80 to 1.00 g.
/ Cm ³ is preferred.

One or more known white pigments can be used in the support, the undercoat layer, the uppermost layer and the backcoat layer used in the present invention. For example, light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate,
Diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, colloidal alumina, pseudo-boehmite, aluminum hydroxide, alumina, lithopone, zeolite, white inorganic pigments such as hydrohaloysite, magnesium carbonate, magnesium hydroxide, styrene Examples include organic plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, organic pigments such as urea resins and melamine resins. Among the above, the white pigment contained as the main component in the ink receiving layer is preferably a porous inorganic pigment, and examples thereof include porous synthetic amorphous silica, porous magnesium carbonate and porous alumina, and particularly the pore volume. Highly porous synthetic amorphous silica is preferred.

As the adhesive, for example, polyvinyl alcohol, vinyl acetate, oxidized starch, etherified starch,
Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, gelatin, soybean protein, silyl modified polyvinyl alcohol, etc .; maleic anhydride resins, styrene-butadiene copolymers, conjugated diene-based copolymers such as methyl methacrylate-butadiene copolymers. Latex; Acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester, polymer or copolymer of acrylic acid and methacrylic acid; Vinyl polymer latex such as ethylene vinyl acetate copolymer Or a functional group-modified polymer latex with a functional group-containing monomer such as carboxyl group of these various polymers; water-based adhesive such as thermosetting synthetic resin system of melamine resin, urea resin; polymethylmethacrylate, polyuret Down resin, unsaturated polyester resin,
Examples thereof include synthetic resin adhesives such as vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and alkyd resin, and they are used in one kind or more.

Further, as other additives, pigment dispersants, thickeners, fluidity improvers, defoamers, defoamers, release agents,
Foaming agents, penetrants, coloring dyes, coloring pigments, optical brighteners, ultraviolet absorbers, antioxidants, preservatives, anti-bacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, etc. It can also be blended.

The method of coating and impregnating the undercoat layer or the back coat layer on the support of the present invention is carried out by various blade coaters,
Various devices such as a roll coater, an air knife coater, a bar coater, a rod blade coater, a short dwell coater, and a size press can be used on-machine or off-machine. Further, after coating or impregnation, finishing may be performed using a calendar such as a machine calendar, a TG calendar, a super calendar or a soft calendar.

The curtain coating apparatus for coating the uppermost layer on the undercoat layer of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of the present invention and is a schematic view of a coating apparatus for coating the uppermost layer. The top layer coating liquid prepared in advance is sent from the coating liquid storage tank 11 to the coater head 1 by the liquid supply pump 12.

The interior of the coater head 1 is composed of a manifold 6 and slits 2, each of which is finished with high precision. The supplied coating liquid fills the manifold 6 and further reduces the influence of the dynamic pressure due to the liquid feeding of the pump 12 in the narrow gap that passes through when it is sent to the slit 2, so that the pressure distribution in the width direction is made uniform. , Lip 3
Further outflow, a vertical curtain film 4 is formed.

The vertical curtain film 4 having a uniform profile in the width direction comes into contact with the continuously running web 5,
It is applied to the web 5. Here, the edge guides 10a, 1
0b is provided not to exceed the width of the coater head 1 and further to the width of the web 5, and the vertical curtain film is formed to exceed the width of the web 5. The vertical curtain film 4 is formed so as to exceed the width of the web 5 in order to prevent thick coating of the coating layer on both ends of the vertical curtain film 4. Web 5
The coating liquid that flows down beyond the width of 1 is collected in the liquid receiving tank 9, returned to the coating liquid storage tank 11, and then applied again. Further, even when the coating is interrupted such as when the web 5 is cut, the coating liquid is collected in the liquid receiving tank 9.

The air flow entrained in the web 5 is shielded at the contact portion between the continuously running web 5 and the vertical curtain film 4 (hereinafter referred to as the "coating portion"), so that the air around the curtain is circulated. Web 5 without vertical curtain film 4 being disturbed
A wind shield 8 is provided to reach the position.
Further, the web 5 is conveyed in such a manner that the roll 7 immediately changes the direction of conveyance of the web 5 to minimize the influence of air entrained in the web 5 on the application portion.

In order to apply the formed vertical curtain film 4 in a stable state, the web 5 is moved to the coater head 1.
The height to the lower outflow portion is required to some extent, but in the present embodiment, the height can be controlled, and the height suitable for stabilizing the vertical curtain film 4 is 60 to 30.
It is 0 mm, preferably 100 to 250 mm, more preferably 120 to 180 mm.

Needless to say, the present invention is not limited to the above-mentioned embodiments, but can be variously modified. In the above-mentioned embodiment, the width of the formed curtain film is larger than the width of the web 5, but this is to prevent the increase of the coating amount at the both ends of the coating layer. If it is small, or if it is not a serious problem, or if it can be solved by adopting the method disclosed in Japanese Patent Publication No. 49-14130, or other method for preventing increase in coating amount, a vertical curtain film is used for the web. It may be equal to the width of 5 or slightly smaller.

The ink referred to in the present invention means the following colorants,
A recording liquid composed of a liquid medium and other additives.

Examples of the colorant include water-soluble dyes such as direct dyes, acid dyes, basic dyes, reactive dyes and food dyes.

As the ink solvent, water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,
C1-C4 alkyl alcohols such as tert-butyl alcohol and isobutyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; alkylene groups such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol having 2 to 2 alkylene groups 6 alkylene glycols; glycerin, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, trie Examples thereof include lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether and triethylene glycol monoethyl ether are preferable. Other additives include, for example, PH adjusters, sequestering agents, fungicides,
Examples thereof include viscosity modifiers, surface tension modifiers, wetting agents, surfactants, and rust preventives.

The ink jet recording sheet according to the present invention is not limited to use as an ink jet recording sheet, and may be used as any recording sheet using a liquid ink during recording. For example, an ink sheet in which a heat-fusible ink containing a heat-fusible substance, a dye or pigment as a main component is applied on a thin support such as a resin film, high-density paper, or synthetic paper is heated from the back side of the ink sheet to remove the ink. An image-receiving sheet for thermal transfer recording that is melted and transferred, an inkjet recording sheet that heat-melts a heat-meltable ink to form fine droplets and performs flight recording, an inkjet recording sheet that uses an ink in which an oil-soluble dye is dissolved in a solvent, photopolymerization An image receiving sheet corresponding to a light and pressure sensitive donor sheet using microcapsules containing a type monomer and colorless or colored dyes and pigments can be used.

The common point of these recording sheets is that the ink is in a liquid state at the time of recording. The liquid ink penetrates or spreads in the depth direction or the horizontal direction of the ink receiving layer of the recording sheet before being cured, solidified, or fixed. The various recording sheets described above require absorptivity according to each method, and the inkjet recording sheet of the present invention can be used as the various recording sheets described above.

Further, the ink jet recording sheet according to the present invention can be used as a recording sheet for heat-fixing toner of the electrophotographic recording system which is widely used in copying machines, printers and the like.

[0046]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.
Further, “parts” and “%” shown in the examples represent parts by weight and% by weight, unless otherwise specified.

The inkjet recording suitability was measured by the following method. [Print density] The print density is made by Sharp (IO-720).
Black, yellow,
The sum of the optical densities of the recorded images on which solid printing of each color of magenta and cyan was performed. The higher the number, the higher the concentration and the better.

[Heavy color bleeding rate] The heavy color bleeding rate was obtained by printing halftone dots with a magenta ink single color and a cyan ink + magenta ink double color with an inkjet printer (IO-720) manufactured by Sharp. Using an image analyzer, the equivalent circle diameter of the dots is calculated according to the formula shown below, and the diameter of the single color dot of magenta ink (M) and the diameter of the double color dot of cyan ink and magenta ink (CM) are calculated. The quality was judged by the ratio (CM / M). The CM / M value becomes 1.0 or more, and a value close to 1.0 has the diameters of the single color dots and the heavy color dots more equal, and the sharpness and color are high, and it is possible to secure the image quality level which has been increasing in recent years. Becomes

[0049]

## EQU1 ## HD = {(4 / π) × A} ^{1/2 In} addition, HD is equivalent to a circle (Heywood Diameter)
ter: unit μm), A indicates an actually measured area (unit: μm ² ).

[Variation coefficient] The variation coefficient is from Sharp (I
O-720) For a dot obtained by printing halftone dots in a single color of magenta ink using an inkjet printer, the coefficient of variation of the equivalent circle diameter of the dot obtained by the above method was determined. The smaller the value, the smaller the variation of the dot equivalent circle diameter, and the better the image quality.

[Shape Factor] The shape factor is made by Sharp (I
O-720) Dots obtained by printing halftone dots with a magenta ink single color and a cyan ink + magenta ink double color with an inkjet printer, using an image analyzer, according to the calculation formula shown in the following formula 2. The shape factor was calculated.

[0052]

[Number 2] SF2 = {(1 / 4π) × (PM 2 / A)} * 100 Note, SF2 is a shape factor (unit :-), A is the measured area (unit: [mu] m ^2), PM around Indicates the length. The closer the dot shape is to the circle, the closer it is to 100, and the better the image quality. Also, the more complicated the surrounding shape, the larger the value,
It causes deterioration of image quality.

[Coating Defects] The coating defects are detected by an optical defect detecting device installed in the coating device, and the defect length relative to the coating length is defined as the defect rate. The coating defects that can be detected by the defect detection device are defects having uncoated portions such as streaks and scratches and excessive coating portions such as stains. Detection is performed with a width of 0.3 mm or more and a length of 2.0 mm.
It can be detected as long as it is mm or more. The length of the defect is a length obtained by adding 1 m before and after the defect in consideration of the margin when deleting the defect portion. For example, even when the actual length of the defect is 0.1 m, The length is 2.1 m.

The support, undercoat layer coating liquid and uppermost layer coating liquid used in Examples and Comparative Examples have the same composition, and are shown below. [Preparation of Support] Formulation: LBKP (freeness of 400 mlcsf) 50 parts NBKP (freeness of 450 mlcsf) 50 parts Light calcium carbonate / talc = 1/1 (* indicated by ash content in base paper) 15 parts * Commercially available alkyl ketene Dimer 0.05 part Commercially available cationic acrylamide 0.03 part Commercially available cationic starch 0.8 part A pulp slurry is prepared according to the above formulation, and a support having a basis weight of 80 g / m ² (absolute dryness) is prepared by a Fourdrinier paper machine. Was made. After the papermaking, calendering was performed using a machine calender device.

[Undercoat Layer Coating Liquid Mixture] Sylysia 470 (Fuji Divison: Synthetic Amorphous Silica) 100 parts PVA117 (Kuraray: Polyvinyl alcohol) 50 parts The solid content concentration shown in Table 1 was adjusted by the above mixture, and an air knife coater was used. The coating amount shown in Table 1 was applied.

[Blending liquid coating composition for the uppermost layer] Finseal X-37B (Soda Tokuyama: Synthetic amorphous silica) 100 parts PVA117 (Kuraray: Polyvinyl alcohol) 50 parts Sumireze Resin 1001 (Sumitomo Chemical: Cationic Dye Fixing Agent) ) 25 parts A solid content concentration of 15% was adjusted by the above formulation.

Example 1 The undercoat layer coating liquid was applied at 7 g / m ² , and the dwell time was adjusted to 2.4 seconds by setting the distance between 1C and 2C to 4 m without the drying step and the line speed to 100 m / min. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Example 2 The undercoat layer coating liquid was applied at 7 g / m ² and the dwell time was adjusted to 4.8 seconds by setting the distance between 1C and 2C to 8 m without a drying step and the line speed to 100 m / min. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Example 3 The undercoat layer coating liquid was applied at 7 g / m ^2, and the 1C-2C distance was set to 12 m without a drying step and the line speed was set to 200 m / min to adjust the dwell time to 3.6 seconds. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Example 4 The undercoat layer coating liquid was applied at 7 g / m ² , and the dwell time was adjusted to 2.4 seconds by setting the distance between 1C and 2C to 12 m without the drying step and the line speed to 300 m / min. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Example 5 The undercoat layer coating solution was applied at 4 g / m ² and the dwell time was adjusted to 3.6 seconds by setting the distance between 1C and 2C to 12 m without a drying step and the line speed to 200 m / min. Then, the uppermost layer coating liquid was applied with a curtain coating device at 11 g / m ² .

Example 6 The undercoat layer coating solution was applied at 10 g / m ² and the 1C-2C distance was adjusted to 12 m without a drying step and the line speed was set to 200 m / min to adjust the dwell time to 3.6 seconds. Then, the uppermost layer coating liquid was applied by a curtain coating device at 5 g / m ² .

Comparative Example 1 The undercoat layer coating liquid was applied at 7 g / m ² , and the dwell time was adjusted to 6.0 seconds by setting the 1C-2C distance to 10 m without the drying step and the line speed to 100 m / min. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Comparative Example 2 The undercoat layer coating liquid was applied at 7 g / m ² , and the dwell time was adjusted to 7.2 seconds by setting the 1C-2C distance to 12 m without the drying step and the line speed to 100 m / min. Then, the uppermost layer coating liquid was applied by a curtain coating device at 8 g / m ² .

Comparative Example 3 The coating liquid for undercoat layer was applied at 7 g / m ^{2 and} then dried, and the coating liquid for the uppermost layer was set off line by a curtain coating device at a line speed of 200.
8 g / m ^{2 was} applied under the condition of m / min.

Comparative Example 4 The undercoat layer coating liquid was applied at 3 g / m ² and the 1C-2C distance was 12 m without a drying step and the line speed was 200 m / min to adjust the dwell time to 3.6 seconds. Then, the uppermost layer coating liquid was applied at 12 g / m ² by a curtain coating device.

Comparative Example 5 The undercoat layer coating liquid was applied at 7 g / m ² , and the dwell time was adjusted to 3.6 seconds by setting the 1C-2C distance to 12 m without the drying step and the line speed to 200 m / min. Then, the uppermost layer coating liquid was applied at 8 g / m ² by an air knife coating device.

Comparative Example 6 The undercoat layer coating liquid was applied at 7 g / m ^{2 and} then dried, and the uppermost layer coating liquid was taken off-line by an air knife coating device at a line speed of 20.
8 g / m ^{2 was} applied under the condition of 0 m / min.

Comparative Example 7 The undercoat layer coating liquid was applied at 7 g / m ^{2 and} then dried, and the uppermost layer coating liquid was offline with a rod coating device at a line speed of 200 m / m.
8 g / m ^{2 was} applied under the condition of min.

Comparative Example 8 The undercoat layer coating liquid was applied at 7 g / m ^{2 and} then dried, and the uppermost layer coating liquid was offline with a reverse roll coating device at a line speed of 2
8 g / m ^{2 was} applied under the condition of 00 m / min.

Table 1 below shows the results of evaluations based on the above evaluations of the ink jet recording sheets prepared in Examples 1 to 6 and Comparative Examples 1 to 8.

[0072]

[Table 1]

As is clear from Examples 1 to 6, in the ink jet recording sheet in which at least two or more ink receiving layers are coated on the support, the coating amount of the undercoat layer on which the uppermost layer is coated is 4 g / m ² or more, the dwell time to apply the top layer and within 5 seconds without a drying step from the undercoat layer coating completed by applying the top layer using a curtain coating apparatus, the printing density, heavy color bleeding rate It was possible to obtain an ink jet recording sheet which is excellent in printing quality as shown by dot diameter variation and dot shape and has no coating defects.

On the other hand, as in Comparative Examples 1 to 4, even when the uppermost layer is coated by the curtain coating device, when the dwell time is 5 seconds or more and the undercoat layer coating amount is 4 g / m ² or less. Caused a coating defect, and the print quality was impaired.
Further, as in Comparative Examples 5 to 8, when the coating of the uppermost layer was performed by a device other than the curtain coating device, print quality was deteriorated and coating defects were observed.

[0075]

According to the present invention, it is possible to obtain an ink jet recording sheet having a high printing density and having excellent image colorability without coating defects, without the image density unevenness due to the influence of the dot diameter variation rate and the dot shape. You can

[Brief description of drawings]

FIG. 1 is a schematic view of a curtain coating apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 1 Coater head 2 Slit 3 Lip 4 Curtain film 5 Web 6 Manifold 7 Roll 8 Wind shield 9 Liquid receiving tank 10a, 10b Edge guide 11 Storage tank 12 Liquid feed pump

Claims (2)

[Claims] 1. The coating amount of an ink receiving layer as an undercoat layer adjacent to the uppermost ink receiving layer is 4 g / m ² or more,
The ink receiving layer of the uppermost layer is applied onto the ink receiving layer of the undercoat layer in a wet state by a curtain coating device within a dwell time of 5 seconds and dried, and at least two or more ink receiving layers are provided on the support. An inkjet recording sheet characterized by: 2. A method for producing an ink jet recording sheet comprising at least two or more ink receiving layers provided on a support, wherein an ink receiving layer as an undercoat layer adjacent to the uppermost ink receiving layer is applied at a coating amount of 4 g / m ² or more is applied, and the uppermost ink receiving layer is applied on the undried ink receiving layer of the undercoat layer within 5 seconds by a curtain coating device, and dried. A method for manufacturing an inkjet recording sheet, comprising: